Ok I have a Question. My brothers 1984 TA is striped, We are Using a Painless Wiring Fuse Block For most of the wiring, But Relays Will be used on Fans, Fuel Pump, Headlights. Well My question is We are going to mount Toggle switches to the sheetMetal dashboard for Fuel Pump On function and also For the Fan will Be using Temp Sensors but a Toggle Switch will be there so that We can Run it full time if need be, Since We are using Relays can The Toggle Switch Just Go To Ground for the on and off Function. Rather than running Power to multiple Switches like Painless does

Please keep Replys related to question not Why we have a sheet Metal dash board ECT,

 

If the hot goes directly to the relay I can see no reason why you could not simply ground the other side of the relay coil through the switch. I'm assuming that the hot to the relay is fused. Probably the Relay Hot Feed is fused and is common to all the relays.

In the case of the fan relay I'll assume you have the temp switch between the relay coil and ground. Just wire the switch in parallel (across) the temp switch.

Frank

 

Yes the Hot will go directly to the relay but I am using Fusible Links instead of fuses.

Yes the fan will have a temp switch in the passanger side head for on fan and either a adjustable on the raditor or a regular tem sensor in the intake. I will have the Ground from the temp sensor T off, One side to fan on to toggle.

I was just wondering if any of these Items will still pull power with no ground, I have seen some auto motive stuff power just not very well with out ground.

 

Yeah, that can happen but when it does it means that there is indeed a path to ground somewhere although it may be a weak (high impedence = high resistance, sort of) ground. In the case of a relay coil I think the risk is pretty low that you will have this sort of problem. That being said, the relay coil is low current (that's the whole idea!) and so even a very weak parisitic ground could cause trouble.

Relays are pretty simple, at least on the coil side. Two wires, normally don't care about polarity, pretty easy to see if there is a weak ground sneak path available. Same goes for the temp switch.

Frank-Bob

 

The Diagram Below is how I am going to Wire the Fans and Fuel Pump, The fans will have a Constant 12v switched by a Negitive Trigger wire that will connect to the Temp switch and a toggel switch so that I can turn the fans on with out the ignition being on.
The fuel Pump will have a Switched Ignition 12V triggered by a Negitive Trigger wire.

I think that would be sufficient. not sure if I should use a diode to prevent voltage spikes across the Relays Coil or not.

 

So then the schematic you show is representative of only the pump circuit, correct?

Do you plan to fuse the pump and relay separate from the rest of the relay circuits?

The only comment on the pump circuit is that a short between the relay and the pump will be hard on the relay contacts. If you power the pump constantly like your fan circuit and switch the ground then only a shorted load (pump) will effect the relay. I know this makes the wiring messy. The fuse will help, the risk is low, figured I had to throw in my 2 cents.

The diode is a good idea. Normally the diode is required when you are using an electronic device to drive the relay coil. The voltage spikes can damage silicon devices. However, the diode could help to increase mechanical switch life too. As you break the relay coil circuit the voltage spikes are generated as the relay coil seeks to dump the energy stored in it. This will cause arcing across the switch contacts which can reduce switch life. The energy stored in the relay is pretty low but diodes are cheap so why not be safe?

Frank

 

Every Relay circuits main Power Will be fused seperatly and Will Be protected with a fusiable link. like a 8ga wire will need a 12ga fusiable link, Fusiable links arent prone to thermal breakdown like a fuse, that is why auto manufactures use them.
I plan to run two relays for the fans 1 per fan since each fan will have its own temp switch and a manuall bypass toggle, but I am wiring the car from scratch with a Painless Fuse block will handle the headlights, Taillights,turn signals, flashers, wipers, marker lights, dome lights. Now The Guages, Ignition, Fans, Fuel Pump's, Nitrous, Line Lock. Will All be Ram using Seperate Relays and induviduly Protected by fusiable Links, That way If I have a problem I know it I look at the Painless Circuits or the Racing Circuits. That way I have less wiring to look through, and don't loose all power to everything at once. I am very very picky about wiring. I hate they way The Factory Cars are wired every thing is intermingled, But it helps them to keep costs down.

My two favorite Electrical Wiring websites are
http://www.the12volt.com/ (Awesome forums and Info)
http://www.madelectrical.com/electrical-tech.shtml (Awesom products and Info)

 

Sounds like you've got it nailed!

I'm an old EE but besdies design capabilities I've got lots and lots of practical experience. I also worked as an auto electrician for a short time. I've been blowing stuff up since I was 13, oh those were the days.

Sounds like your going to have a very clean and high quality electrical system.

Frank

 

Thanks I hope so. That is what I am trying for. I really wish I had the knowledge to design more complex circuts, and have a better understanding of the more complex stuff like designing stuff like craig Moates (autoprom) but this is just a hobbie and what I do know is the basics of stuff but I must learn to crawl before I learn to run maybe One day I will learn the more complex side of things.

I just picked up Electronics when I was 12 helping my brother install his stereo system in his car, And I caught the Electronics, Wiring Bug. I have also learned fiberglass molds and a few other neat tricks, now At the ripe age of 27 it really comes in handy on projects like this.

 

Why not let the ECM control the fuel pump and fans with an over ride switch for the fans? Is there a master relay for the 12 volt feed to the relay bank or is it straight from the battery. Makes no sense to run fans when engine is dead. That will cool the radiator but nothing else. Then you crank a hot engine and slam cold water into it (not good).

 

Well the ECM is long gone in favor of a BG 750 Mighty Demon, the dash board has been replaced with a peice of .025 sheet metal, The seats are Poly Race seats, The gas tank is gone in favor of a 12 Gallon Fuel Cell, Battery Relocated to rear with a Remote start solinoid, and a flaming river Cut off Switch Mounted through the tailight so that when it isn't on the track just remove the passanger side light and Put the Street Tailight in. so we also have Spohn SFC's Jegs 8 point roll Cage, Simpson Belts, ECT will be going in to this. It will still pass a state inspection and be street driveable but Will Be More Strip Friendly.